Enzalutamide (MDV3100) is an oral androgen receptor inhibitor which is capable of preventing the growth of a castration-resistant prostate cancer promoted by androgen and is very useful.
As a form of an enzalutamide bulk drug, development of a solvent-free crystal form (hereinafter, also referred to as “A-type crystals”) is in progress, but it is suggested that there is a possibility that enzalutamide is often formed as a solvate which is a solvent addition form in the process of crystallization, and the details thereof are not known (Patent Documents 1 and 2).